Mass data storage systems, such as disk drives and optical drives, are generally used in computer systems to store large amounts of information for potential use by a host computer. This information may include, for example, program files and/or data files. When the host computer wishes to retrieve information from the storage system, such as when a user wishes to run a certain program, the host causes the information to be transferred from the storage system to the host's random access memory (RAM). Once transferred, the information may be used by the host in the appropriate manner. Some mass storage systems also allow the host to write information to the storage system.
To perform their designed function, data storage systems must include a storage medium capable of holding stored information in a readable form. For example, magnetic disk drives generally store information on disks having at least one surface coated with a magnetic material. Information is usually stored on the storage medium in a form that is unrecognizable by the host computer and that is a function of the particular medium being used. Therefore, after the information is read from the medium using a transducer, the information must be converted to a form that can be used by the host computer before it is transferred to the host's RAM.
To perform the information conversion function, data storage systems generally include a recording channel between the storage medium and the host computer. The recording channel receives the signal read from the storage medium and converts the signal to a form that is recognizable by the host computer. In storage systems that allow the host to transfer information to the storage medium, the recording channel may also be operative for converting information from the host computer into a form that can be stored on the associated storage medium.
A recording channel may be required to perform any number of different functions. The functions that a particular recording channel is required to perform are generally dependent on the type of storage medium being used and the manner in which information is stored on the medium. For example, magnetic disk drive systems generally store information in the form of magnetic polarity transitions, i.e., the surface of the disk includes a series of polarity reversals from a north-south orientation to a south-north orientation, and vice versa, that can be detected by a transducer. The channel, therefore, must be able to detect the polarity transitions in the signal read by the transducer. In addition, the channel should be capable of recovering timing information from the read signal to be used in clocking the resulting data signal. Further, the channel must be capable of removing any encoding from the signal after the transitions have been detected and timing has been restored.
Recording channels generally include a plurality of adjustable parameters that effect the overall operation of the data storage system. In this regard, the performance of the storage system depends on the determination of optimal values for the various channel parameters. Therefore, it is important that a method be provided for tuning the channel parameter values in a data storage system to achieve an acceptable performance from the system.
In the past, recording channels were generally tuned using a brute force method. That is, an array of channel parameter settings were applied to the channel one at a time, often manually, and the resulting system performance was measured. When a set of channel parameters was found that resulted in acceptable system performance, these values were stored for later use by the channel. Because the brute force method tests all or most of the possible combinations of parameter values, it is extremely slow and significantly increases the total manufacturing time for a data storage device. Increased manufacturing time creates higher costs which results in reduced profits and/or increased prices to customers.
Therefore, a need exists for a method and apparatus for rapidly and accurately tuning parameter values in the recording channel of a data storage system.